SERPINE1 and glycogen storage disease VI: In addition, FC concentration is affected by disease-independent factors such as age and comorbidities and shows a considerable day-to-day variability.41 There are no optimal cut-off values to define active and inactive disease or to predict clinical and endoscopic remission or treatment response.9,42 FC level is localisation dependent as it frequently shows normal values in CD located in the small bowel and cannot differentiate between CD and UC.10,43 Our preliminary results showed that faecal PAI-1 was higher in patients with colonic and ileocolonic disease localisation.